The Collaborative International Dictionary
indigo copper
Covelline \Co*vel"line\ (k?-v?l"l?n), Covellite \Co*vel"lite\ (-l?t), n. [After Covelli, the discoverer.] (Min.) A native sulphide of copper, occuring in masses of a dark blue color; -- hence called indigo copper.
Wiktionary
indigo copper
n. covellite